X-Ray Sources: Sco X-1

In fact, the moon is the LEAST luminous extra-terrestrial X-ray source known with an
X-ray luminosity of 7 x 1011 erg per second! On the basis of the known
flux of solar X-rays, the flux from the moon is estimated to be about 0.1 to 1.0
photon cm-2 sec-1.